Centrifugal fan



NOV. 1, 1938. J ROCKWELL 2,135,053

CENTRIFUGAL FAN Filed Aug. 24, 1937.

Nov. 1, 1938 UNITED STATES PATENT or-"rrcs 2,135,053 ENTBIFUGAL FAN JohnA. Rockwell, Phoenix, Ark. Application August 24, 1937, Serial No.160,868 1 Claim; (CI. 23. 127) This invention relates to centrifugalfans or pumps of the squirrel cage type and particularly to those fansor pumps having blades ex-- tending approximately parallel to the axisof rotation of the fan or pump. This class of fan is open to theobjection that (the air pumped through the blades by centrifugal forcetends to hug the air inlet flange ring at the margin of the air inletopening, creating high air pressure relatively adjacent the annular wallof the air inlet opening. This increases resistance and the air is notdistributed evenly over the length of the blades, thus decreasing theefliciency of the fan and requiring a larger fan operating at slowerspeed. Furthermore, the air is given a rotary motion causing a variationin velocity of the air entering the inlet of the fan.

The object of my invention is to make it pos-' sible to operate fans ofsmaller diameter at higher speeds and yet secure the same results aswould normally be secured by oversized fans,

which must be operated at slower speed to obtain the same capacity.

My invention is illustrated in the accompanying drawing wherein:

Figure l is a diametric section through a fan and casing thereforconstructed in accordance with my invention.

Figure 2 is an end elevation partly in section of the fan and thepartition plates therefor removed from the casing.

- In the drawing, in designates a fan casing as,

commonly used with squirrel cage" fans, the casing having the inlet lldefined by the inlet flange ring II. The outlet of the casing isdesignated l3. Extending longitudinally through the casing Ill is ashaft it having thereon the back plate l5 carrying the axially extendingblades l6, as many as may be desired. Sofar, the parts described aresuch as is commonly found in squirrel cage fans.

My invention consists in disposing within the space defined by theblades, a plurality of radial partitions ll shown as four in number,though I do not wish to be limited to this number of partitions,dividing the low pressure space of the fan into four compartments orducts. The walls ll prevent the air from rotating as it enters the inletopening of the fan casing and when it is within the low pressure areaofthe fan. The air cannot start rotating until it reaches the fan bladesbecause these radial partitions I'I extend radially outward to a pointclosely adjacent to theinner edges of the blades and extend from a pointclosely adjacent tothe plate I! out to the inlet ring I2.

In order to prevent the .air from being urged by the centrifugal forcetoward the inlet ring, thus preventing proper distribution of the air 5along the fan blades, I divide each of the compartments formed by thepartitions ll into a plurality of ducts III by walls I9. Each partitionor wall I! extends axially inward from the inlet and then curves gentlylaterally or radially outward to points adjacent to the inner edges ofthe fan blade It. The walls l9 may be supported in any suitable manneras by the radial partitions i1 and these radial partitions or walls I!are supported in any suitable manner as by the inlet flange or ring l2.It is to be noted that the radial walls "and the funnel-like guide wallsI! extend to the front wall or flange l2 of the fan casing and that theinner ends of the walls I! extend to the edges of the radial walls llclosely adjacent to the inner edges of the fan blades. By the use ofthese guide walls l9, the space defined by the fan blades and the rearwall I 5 is divided into a plurality of concentric inlet ducts whichlead directly to the fan blades and these partitions or walls guide theentering air column in equal amounts and distribute it evenly to the fanblades and prevent the air from hu ging the outside inlet wall orflange, and taking a short cut to and through those portions of theblades which are adjacent said ring l2, while the radial partitions I!prevent any whirling motion being given to the air.

Of course, the shaft I 4 is supported in suitable rings and I haveindicated these bearings by the numerals 2|.

Thewalls' ll define ducts which distribute the air column equally overthe inlet until it reaches fan blade I. By dividing the air equallyacross the inlet flange l2, it is possible to prevent all 40 the airfromentering at .a higher velocity at the space directly adjacent to theflange ring II. The centrifugal pull created across the inner surface ofblades I will be equally felt in all pockets or ducts formed by thewalls I9 and I'I. By ca ying this centrifugal pull evenly across theface of the inlet, the air is evenly distributed and segregated at itssource, namely, the inlet flange.

The result obtained. by dividing the inlet into quadrants, as shown,creates four pockets. By the inserting of guide vanes it, the result isa total of twelve pockets, such 88 is designated by It can then be seenthat the centrifugal pull created by I! will divide the inlet diameterinto twelve separate sources of air supply.

To obtain a given capacity, for instance, and using a hypotheticalcase-on one hand we have a fan operating at 1000 R. P. M. to produce1000 cubic feet of air current; on the other hand we have a smaller fanoperating at 2000 R. P. M. to produce the same amount of air. The secondfan would be half the size and half the weight and would still producethe same amount of air. Larger fans operating at slower speed are: .notusually troubled with the faults I am'attempting to correct, but aslarger fans have more weight and take up more space, this inventionwould permit a saving in both these items.

While I have illustrated certain details of construction and a certainspecific arrangement of parts, I do not wish to be limited to theseexact details or arrangement as obviously these might be varied in minorrespects without departing from the spirit of the invention as definedin the appended claim.

. What is claimed is:

A fan of the "squirrel cage" type, including a casing having an inletopening in its front wall and an outlet opening in its side wall, ashaft extending centrally through the casing, a back plate mounted uponthe shaft adjacent the inner wall of the casing, a plurality of axiallyextending blades carried by said back plate and extending to the frontwall of the casing, a plurality of radially disposed partition wallswithin the space defined by the shaft and the parallel blades of thefan, the partition walls being held from rotation with the fan andextending from the front of the casing to the rear thereof and from theshaft to the inner edges of the blades, said radial walls dividing thespace within the fan into a plurality of compartments, and a pluralityof walls disposed between each pair of partition walls and extendinginward from the inlet opening of the fan in concentric relation to eachother and approximately parallel to the axis of rotation of the fan andthen curving laterally outward and extending radially in planes radialto the axis of rotation but at right angles thereto and terminating atthe outer edges of said radial walls, the said concentric walls formingducts and being attached to the radial walls.

JOHN A. ROCKWELL.

